Tubing



Sept. 17, 1935- B. L. QUARNSTROM TUBING Original Filed May 21, 1934 v INVENTOR.

50W 1 Ol/fimvsrfion.

ATTORNEY.

Patented Sept. 17, 1935 'UNITED STATES I TUBING Bert L. Quarnstrom, Detroit, Mich assignor to Bundy Tubing Company, Detroit, Mlcln, a corporation of Michigan Application May 21, 1934, Serial; No. 126,858.

Renewed August 14, 1935. In Canada 3 Claims. (on. 13-1-15) This invention has to do with tubing and it relates particularly to a tube structure involving a multiple wall. More particularly, the invention is directed to improvements in a tube 6 of the type covered in the patent to H. W. Bundy No. 1,431,368 of October 10, 1922. This application is a continuation of my application, Serial No. 515,826, filed February 14, 1931.

I The object of the invention is to provide an improved seam or joint which has an increased strength. A tube made in accordance with the invention is capable of withstanding high internal pressure, and the seam structure is such as to not pull out or break under such internal pressures. Moreover, the seam structure is such as to advantageously permit of working a finished tube and especially cold working the tube, as by drawing it to reduce its size and/or bending it into shapes. This will be touched upon in more detail in the following description.

In the accompanying drawing:

Fig. 1 is a sectional view taken of a tube involving the improved structure;

Fig. 2 is a sectional view taken through a strip of metal from which the tube may be formed.

Fig. 3 is a view of a strip of metal from which the tube may be formed, which strip is provided with a covering or plating.

Fig. 4 is a view of a seam or joint formed of a covered or plated strip.

The tube comprises essentially a strip of metal stock fashioned transversely into hollow cross sectional form with plural ply walls. As shown. in Fig. 1 the stock is fashioned to form an inner ply I, an outer ply 2 and the ends of the stock substantially meet an offset or jog 3. This general structure is covered by the patent above mentioned.

The improved seam structure involves the formation and association of the jog and the edges of the stock. As shown in Fig. 2 the strip of stock from. which the tube may be made is provided with beveled faces near its edges. Thebeveled face at one edge is illustrated at 4 while the beveled face at the opposite edge is on the opposite side of the stock as illustrated at 5. The stock is fashioned through slightly more than 720, and thus the beveled edges overlap each other. The fashioning of the stock preferably exceeds 720 to an extent substantially equal to the dimensions of the beveled faces. The olfset or jog 3 is formed at such an angle that the beveled edges of the stock substantially coincide therewith when brought into abutting relation with the jog. This angle is preferably March one which is not abrupt; in other words, the Jog lies at a relativelyslight angle to a tangent meeting the tube wall at a radial line cutting the jog substantially centrally.

The tube structure thus described may be completed by the uniting of the inner and outer plies and uniting the beveled edges of the stock to the jog by any suitable sealing metal. Such sealing metal may be solder; that is, the ordinary solder composed largely of lead and tin, or silver solder, 10

or the like, or the so-called hard solder or brazing alloys, or copper or others.

Such a seam offers high resistance to internal pressures. Due to the fact that the jog is at such a slight angle it effectively resists high in- 15 ternal pressures as it resists being straightened out or pulled out. Moreover, it is abutted on opposite sides by the beveled edges thus further resisting rupture. One advantageous formation is that of forming the jog at such an angle and 20 beveling the edges at such formation that the opposite edges overlap. In other words, the inner and outer edges cross a radial line drawn substantially through the center portion of the j E- 25 The beveled edges may be provided in a'number of ways. One manner is that of compressing the stock. However, beveled edge formation may be provided by shearing oil some of the metal from a square edge.

In cold working the tube, the beveled edges do'not press or cut into the metal of the jog as would be the case with a square edge, and thus, the seam remains strong even after such cold working. Moreover, due to the slight angle 35 of the jog, the metal at this portion is not strained or weakened in any material degree. Likewise, the beveled edges do not cut into the metal of the jog when the tube is bent, nor is the jog liable to be pulled out when the tube is 40 bent while the same is on the outside of the curve.

The sealing metal may be advantageously carried by the strip before the same is shaped into tube form so that when subjected to heat the 45 sealing metal becomes molten to effect uniting of the abutting parts with or without the addition of other sealing metal. In this event the structure lends itself to the formation of a strong seam. Fig. 3 illustrates a strip of stock having a covering or plating of sealing metal, as illustrated at III. when the edges are compressed to effect the beveled formation the sealing metal In covers the beveled face, as shown, leaving but a slight portion, as illustrated at I I, which is bare. when this well as between the plies. This is advantageous particularlyinatubestructure utilisingcopper as a co'ating and sealingmetalwherein the strip iscoveredorplated withalayeroioopper-previous 'tobeingformed ina tube.

The stripstockformingthebasicmaterialo the tube may be of ferrous metal, such as low carbon steel. The advantages of the tube structure appear more pronounced where copper is used as a sealing metal in connection with steel strip over some other metals having a lower fusing point, as for example solder. This appears to be due to the fact that copper makes a stronger bond and alloys with the steel more readily than the metallic elements in solder. Bolder, as used in this connection, refers to a mixture composed largely of lead and tin. For example, a tube made of steel strip coated and sealed with copper shows by test to have an internal bursting premure of about 45% greater than the bursting pressure of a similar steel strip copper coated tube having a seam structure where the edges are not beveled, such as illustrated in the above mentioned Bundy patent. Where solder (tin and lead) is used on steel strip, a tube made in accordance with this invention shows by test to have an internal burstingpressureabout25% greaterthanasimilar soldered tube but having straight or non-beveled edges and an abrupt offset as shown by the Buncly patent. As mentioned above, this appears to be .due to the greater binding qualities of copper. It is thought that this increased strength comes about, at least in part, not only on account of the fact that the offset is not abrupt but also because the beveled edges unite to the oflset over a substantial area which is greater than the radial extent of the oil'set. The new tube structure also makes for a tube capable of better withstanding torsion and twisting strains and bending operations, as the nature of the seam is such as to resist the tendency of the seam to open up or split lengthwise of the tube. The seam structure minimizes the longitudinal crack or groove, thus materially aiding in the eifecting of a fluid tight seal between the tube and a fitting with which it may be used.

A tube made in accordance with the disclosure herein and embodying steel strip with copper used as the coating and sealing metal is preferably made from copper coated or plated steel strip fashioned into the hollow cross-sectional form and then subjected to heat in a furnace in the presence of a non-oxidizing or reducing environment. The furnace may contain a non-oxidizing or reducing atmosphere such as hydrogen or a gas obtained by cracking ordinary illuminating gas and which has non-oxidizing and/or reducing characteristics. The resultant tube shows a bright copper finish inside and out with the seam and plies united thereby and with the tube free from sdeleterious oxides upon its completion.

I claim: v

1. A tube comprising a copper coated .strip of steeLtheedgesofthestockbeinginitiallybeveled for a substantial width from opposite sides of 10 the stock, with the copper coating preserved on the beveled faces, said strip being fashioned through more than 720' into hollow cross sectional form with double ply walls. and with the beveled edgu overlapp g each other circumfer- 15 entially substantially throughout their entire width and separated by a portion of an intervening ply, said portion of the intervening ply being in the form of an offset on a gentle angle as regards the general direction of extent of said to walls and substantially corresponding in shape to the beveled faces of said edges, said beveled faces contacting. substantially throughout their entire surfaces with opposite sides of said offset portion, said plies being secured together and the beveled 25 edges secured to opposite sides of the offset by the fusing of the copper coating. I

2. A tube comprising a metal strip having its edges initially beveled for a substantial width and from opposite sides of the strip, the strip and beveled faces being coated with a fusible sealing metal and the strip being fashioned through more than 720 into hollow cross-sectional form'with plural ply walls, the beveled edges overlapping each other circumferentially throughout their entire width and separated by an intermediate portion of the stock offset to correspond in shape to the beveled faces of said edges, said beveled faces contacting substantially throughout their entire surfaces with opposite 4o sides of said offset portion, the plies being secured together and the beveled edges secured to opposite sides of the offset by the fusing of the coating metal.

3. A tube comprising a metal strip having its so edges initially beveled for a substantial width and from opposite sides of the strip, said strip being fashioned through more than 720 to form a plural ply tube with inner and outer beveled edges overlapping circumferentially substantially to throughout their entire width, with an intermediate portion of the stock between the beveled edges offset to correspond in shape to the beveled faces, said beveled faces contacting with said oil'set portion substantially throughout their en- 6 tire surfaces and being secured thereto by fusible sealing metal between said offset and beveled faces.

BERT L. QUARNSTROM.

substantially 35 

